Herbicidal compositions and methods of preparing them

ABSTRACT

THE COMBINATION OF CERTAIN RESINOUS AND/OR WAX-LIKE MATERIALS WITH VARIOUS AGRICULTURAL HERBICIDES IN AN INERT, POROUS CARRIER REDUCES THE LEACHING OF THE HERBICIDE FROM THE UPPER 10 CM. OF SOIL AND LOSSES OF HERBICIDE DUE TO VOLATILIZATION AND THUS INCREASES THE EFFECTIVE FIELD LIFE OF THE HERBICIDE

United States Patent 01 3,725,031 HERBICIDAL COMPOSITIONS AND METHODS OFPREPARING THEM Leslie L. Balassa, Blooming Grove, N .Y., assignor to3,725,031 Patented Apr. 3, 1973 "ice As a general rule, herbicides arediluted with either a liquid or a solid diluent or adsorbed on a porouscarrier. In particular, selective herbicides which are applied to thesoil are often adsorbed on a coarse granular carrier which facilitatestheir application. The characteristics of the car- No f g sg g g ggf fi3:5 g2 53 2 912 rier can significantly influence the stability of theherbicide m CL o 5 and its release to the soil. Granular attapulgitetype clays Us, (1 71.405 4 Claims are the most commonly used carriersfor soil application; however, other materials e.g. expanded vermiculiteor ABSTRACT OF THE DISCLOSURE 10 corncob grits, have also beensuccessfully employed as The combination of certain resinous and/orwax-like cirlriers herbficidesilThe g g aamfiulgites Wit}; materialswith various agricultural herbicides in an inert, g fi ig ig i i gg g fg i i ia many 0 g Gamer reducfes g of i ig g g Herbicides applied to thesurface of the soil are exposed t e R 10 0 an 05868 O 6 He 15 toleaching by rain water and volatilization by air currents volatilizationand thus increases the eifective field life and the heat of the sun whenapplied to Subsurface the of the herblclde' herbicides are in directcontact with the soil and are therefore affected by the chemistry andthe microbiological This invention relates to an improved herbicide andlife of the soil. Dieamba 9 Y- heIlZOie more particularly to aherbicidal composition capable of aeldl has relahvely 10W sehlhlhty 111Water- The ee maintaining its elfectiveness over an extended period ofof Dleamha, however, Show eellelderahle Water solublhtyti In contactwith the soil, especially with high pH soil, Di- Virtually every cropand ornamental plant is affected eamhe f0fmS Water h e Sells Which are py eby weeds which compete for space, food, and light. The slpeted y h1r1' 1gat10n Water P even y h eradication and control of weeds is aneconomic necessity 25' molstufe, fl h vetl Dlcamba is carried to lowersoil which can be accomplished by the use of herbicides. A depthshefhleldal effect is lf 10st great number of herbicides are known in theart and are other hefhleldes such h CaSOIOh 0r Dlehlohevnll nowcommercially available. As is known in the art, manydlehlorohenlenlmle), While Y Slightly Soluble in wat of these are quiteselective and exhibit specific herbicidal are too Volatile to l'emalflWlth the carrier 111 the S011 e activity for certain classes of plants.Q ehohgh t0 pp Weed growth throughout the gfOWlhg A number of factorsenter into the performance of any p particular herbicide. The chemicalstructure and nature The eholee of earner Whlle p i h With regard to ofthe herbicide will determine whether or not the heradsorbeney as foundto ve y mlmmal ff n he bicide is efiective and the type of plants withwhich it is rate of soluhlhty and volatlhty and 011 the consequent fftiv loss of the herbicide by dissipation to the soil or to the Thephysical characteristics of herbicides also are ime The Size e theWeight of the f e granules portant. It is essential that significantquantities of the however lmpehtaht 1h eohtrohlhg the appheaheh P pherbicide be retained in the top 5 to 10 centimeters of hes of theherhleldessoil for maximum elfectiveness against weeds. Further, if Itnow e follnd that the eS Can be coma substantial amount of the herbicidepenetrates beyond 40 h ee1' ta111 feSlIlOllS Pr ke mater1al s and thetop 10 centimeters of soil, there is danger that the crop lheofpofeted111 a P 011$ earner t0 I I e herbicidal plant ill b d d A di l h l il dcompositions of controlled water solubility and volatility. watersolubility characteristics of the herbicide can be he Preferredmateflale are these j h which the herquite critical. Any loss ofherbicide from the upper layer hleldee are eompatlhle to form Selld50111110 lq of soil, whether by volatilization or by dissolution and aeohhhheus Water 111S0h1h1e d t osewhlch form soil penetration, gives acorresponding loss in the ability a Wax yp film Whleh holds e herbleldesin a micellar of the herbicide to control weed growth. Such lossesnecesresitate reapplication of the herbicide during the growingHerbicides which can be employed in the composition season atconsiderable cost. in the present invention are shown in Table I.

TABLE I Chemical name Formula Trade name 2-methoxy-3 G-dlchlorobenzoicacid C O OH Dicamba.

o1- OCH:

2, fi-diehlorobenzonltrile 01 03501-911 m m l b nil 4,G-dinitro-o-sec-butylpheno1 EDNBP.

TABLE I-Continued Chemical name Formula Trade namez-chloro-ethylamino-6-isopropy1am1no-1, 3, 5-triazlne (I11 Atrazine.

I CH-NH-C C-NH-O H;

W CH: N

2, S-dichloroallyl N, N-dflsopropylthiolcarbamate C H; Avadex.

C1 C1 0 OH-CH;

I I I GH=COH:SCN\

(i1 H-C H: C H;

Polychlorodicyclopentadiene isomers (chlorine content 60-62%). Bandane.

4-ch1oro-2-butynyl N-(3-chlotophenyl)carbamate (I: Barban.

-NH-c-o-cm-cEc-cmo1 Isopropyl N-(3-chlorophenyl)carbamate fl) /CH; CIPC.

Q-NH-C-O-CH I 01 4,6-dinotro-o-cresol sodium sa OzN (I)Na DNC.

I OzN Dimethyl 2,3,5,6-tetrach1oroterephthalate (I O O OH; Dacthal-1,3-bis(2,2,2-trichloro-1-hydroxyethy1)urea Dichloml urea.

O Ch-CH-NH N-(3,4-dichloropheny1)methacrylamide CH (31 Dicryl.

a I CHpC-(fi-NHQ-Cl 2,5'djchIoro-3-nitr0benZ01c acid C O OH Dinoben.

N,N-dimethyl-2,2-dlpheny1acetamide Diphenamide.

TABLE I--Contlnued Chemical name Formula Trade name 2, 3, 4, 5,6-pentachlor0phenol (J11 PCP.

2-ch1oro-4, 6-bls(lsopr0pyIamln0)-1 3, E-trlazlne- (Ill Propazlne,

Us: 1']! 1} CH CH-NH-C C-NH-CH CH; N CH:

2-chloro-4, 6-bis (ethylamlno)-1, 3, IS-trlazlne (I31 Sl mming,

l r CgHs-NH-C C-NH-CgH Methyl N-(3, 4-dlehlorophenyD-carbamate Cl 0Swap,

II 01- -NH-C-OCH;

2, tdlchlorophenoxyacetlc acid Cl 0 2' ll o1-Qo-cm-c-onN-(l-naphthyD-phthalamlc acid (I) Alana);

J) NH C-CH 3-amino-2, li-dlchlorobenzolc acid (III. Amibm C-OH Cl NH,

The resinous and/or waxy materials useful for the purposes of thepresent invention may be described as members of the group of waxes,resins, bitumens, tars and pitches. Typical waxes include carnauba,beeswax, candelilla and other vegetable and insect waxes, hydrogenatedfatty-acid glycerides, hydrogenated castor oil, ozokerite (Hoechst WaxS) and oxidized ozokerite waxes (X22 of Hoechst Chemical Co.) and theirmodifications, parafiin waxes, oxidized parafiin waxes, andmicrocrystalline waxes (Multi-wax W-445, Witco Chemical Co.). Typicalresins include wood and gum rosin, rosin esters, e.g., pentacrythritolester of rosin (Pentalyn 255 of Hercules Chemical Co.), te-rpene resins(Piccolite A- 115 of Pennsylvania Industrial Chem. Corp.), gum damar,gum copal alkyd resins, oil modified alkyds, polystyrene (Dow resinPS2), polyacrylates and polymethacrylates, cellulose esters and ethers(ethyl cellulose, 7 cps. grade, Hercules Chemical Co.) polyvinyl estersand ethers and shellac. Typical bitumens include gilsonite, petroleumasphalt (Pioneer 180 and Pioneer 220 of Witco Chemical Co.), oxidizedasphalt (180/200 melting point, Humble Oil and Refining Co.). Typicaltars and pitches include coaltar and coaltar pitches, wood creosote,wood pitch, and bone pitch.

Useful inert carriers for the composition of the present inventioninclude expanded vermiculite, sintered clay granules, attapulgite clay,corncob grits, and coke granules. Other similar porous carriers re knownin the art.

One particularly superior carrier material is commercially availableunder the name True-sorb. This material comprises calcined clay-sericitegranules, commonly of 24+48 mesh (Tyler) grain size, and has a typicalchemical analysis as follows:

Spectrographic analysis confirmed the chemical analysis and additionallyindicated a small titanium content and traces of lithium, copper,chromium and manganese. The material exhibits a pH of 7-7-2, has adensity of 38 lbs./ ft. and a lube oil absorbency of 79% A suitablemethod for the preparation of the herbicides composition of the presentinvention comprises dissolving the herbicide and the selected protectivematerial in a volatile solvent in which both are soluble and effectinghomogenous solution of the materials. If necessary, heat may be appliedto assist in forming the homogenous solution. The solution is thenabsorbed onto a suitable porous carrier of the type described and thevolatile solvent is evaporated. This leaves the herbicide in combinationwith the protective material in intimate contact with the carrier. Therelease properties, the solubility and the volatility of the herbicides,are then controlled by the tar pitch additionally possesses sufiicientmoisture resistance to serve as a protective agent against bothhydrolysis and microbiological degradation. Accordingly, coal tar pitchis one of the preferred agents for incorporation in combined factors ofthe nature of the protective material, the composition of the presentinvention. the ratio of herbicide to protective material and the na- Thecombinations of any of the aforementioned herture of the carrierrelative to the materials absorbed bicides with any of theaforementioned protective matethereon. rials and carriers are effectivefor the purposes of the pres- Additional factors which influence theeffective fieldent invention. In the example which follows, 100 gramslife of a herbicide are its oxidative character and its reof herbicideand 100 grams of protective material were sistance to microbiologicaldegradation. The herbicides of individually dissolved in solvent to form50% solutions. the present invention may be protected from microbiolog-The solutions were heated slightly to insure complete disical oroxidative degradation through the inclusion of solution of the solutesand were blended while still hot. bactericides, fungicides andantioxidants in the basic com- The resulting combined solution wasabsorbed on 800 position. Typical antioxidants for this purpose arehygrams of porous granular carrier which had been predroxyanisole.heated to about 50 C. The solvent was evaporated at a Examples of agentsuseful for minimizing microbiologtemperature below 50 C. with constantmixing of the ical attack are as follows: granular mass to provideapproximately 1,000 grams dry Copper compounds-Copper salts of longchain fatty weight of the herbicidal composition. The followingmateacids, including copper oleate, copper stearate and copper 0 rialswere employed.

TABLE II Example Herbicide Protectant Solvent Carrier I DicambaPiccoliteA-115 Carbon tetrachloride Expanded vermiculite. II PiccoliteA-115 Toulene- Attapulgus clay. III Wood resin d0 Do. IV Do. V Do. zedasphalt "do- Do. Do. Do. Do. Control B Dicamba Toluene Do. Control 0...-Dichlobenil. (10.. D0.

octoate; copper naphthenate; and copper 8-hydroxyquinolinolate.

Phenol compounds-Phenol and the oil or hydrocarbon solvent solublephenols and derivatives; halophenols, particularlyo-benzyl-p-chlorophenol (Santophen I made by the Monsanto ChemicalCompany); o-phenylphenol; chloro ortho phenylphenol; pentachlorophenol;tetrachlorophenol; chloroxylenol; chlorocresol; chlorobenzylphenol;methylene-bis (tri-chlorophenol); and the salts of the foregoing whichare soluble in the herbicides; alkyl phenols having an alkyl group of2-28 carbon atoms in the molecule including the various cresols, 0-, andp-ethylphenol, p-isopropyl phenol, p-tertiary-butyl phenol, 2-methyl-4-dodecyl phenol, o-hexadecyl phenol.

Organo-mercury compounds.-Phenyl-mercury acetate.

The foregoing compounds are introduced into the composition of thepresent invention by dissolving them or dispersing them in theherbicides, in the protective matrix, or in both, in an amount of fromabout 0.01% to about 10% (by weight, based on solvent-free herbicidalcomposition). They may also be employed by dusting spraying or coatingthe surface of the granular composition. The preferred method, however,is to include the additive in the matrix or in the herbicide for maximumeffectiveness.

Coal tar, pitch and wood creosote contain sufficient of the abovephenolic compounds to provide the desired bacteriostatic and fungistaticproperties to be suitable as part or all of the protective material forthe herbicides. Coal Appropriate solvents for Dicamba (2-methoxy3,6dechlorobenzoic acid) and Dichlobenil (2,6-dichlorobenzonitrile) includebenzene, toluene, and carbon tetrachloride.

Topsoil was packed into eight polyethylene columns (5 cm. in diameter x25 cm. deep). A one gram sample from one of Examples I through VI andControls A and B was placed in each of the columns and thoroughly mixedinto the top one centimeter of soil. The eight columns were held in avertical position and were sprayed with distilled water for 15 minutesevery 12 hours. Each such spraying corresponds to a rainfall of 0.5 cm.over the column surface. This procedure continued for 21 days duringwhich period the columns were maintained at 25 C. and humidity. At theend of the 21 day test period, the columns were cut into 10 separatesections (of 2.5 cm. each) with minimum disturbance of soil material. Ineach soil section, 10 soybeans were planted, with each being completelycovered by the soil material. The seeded soil sections were then placedin an incubator at 25 C. and 98% humidity. After 14 days the soybeanswere removed from the soil sections and examined to determine the effectof the herbicide. The results of these tests are set forth in Table III.The column Soil Section sets forth the distance from the top of the soilcolumn in centimeters at which the section was taken. The numericalresults reported in the table represented the number of soybeans showingherbicidal injury, a value of 0 indicating no damage to soybeans in thatparticular soil section and a value of 10 indicating injury to all ofthe soybeans in that particular soil section.

TABLE III In'ur to so bean Soil section 1 y y depth in em.- Control AControl B Ex. I Ex. II Ex. III Ex. IV Ex. V Ex. VI

As is evident from the data of Table III, the herbicide control withoutprotectant caused plant injury throughout the 25 cm. soil column, withthe greatest plant injury occurring at depths below 12.5 cm. Theherbicide compositions of Examples I through VI caused little or noinjury at depths at excess of 12.5 cm. and by far the greatest injuryoccurred in soil samples of less than 10 cm. depth. Thus, thecompositions of the present invention retained a high degree ofherbicidal activity in the upper 10 cm. of soil where such actiivty ismost important without significant injury at depths below 12.5 cm.

Dichlobenil is characteristic of the herbicides exhibiting excessivevolatility, albeit, it is comparatively resistant to dissolving. Toillustrate the improvement of the present invention with Dichlobenil,two gram samples of the materials of each of Examples VII and VIII, andof Control C were maintained at 50 C. under identical conditions. Every24 hours the samples were weighed and the loss in weight determined. Theresults of these tests are set forth in Table IV.

TABLE IV Cumulative herbicide loss, percent of original Elapsed time,days Control Ex. VII Ex. VIII As is evident from the data of Table IV,the composition of the present invention has a very significantlyincreased life as compared to the controlled example.

While the method described previously for the preparing of theherbicidal composition of the present invention is the preferred method,other effective techniques are available. Thus, satisfactory results maybe obtained by applying either the herbicide or the protective materialto the porous material individually from solution coupled withevaporation of the solvent and then applying the other componentsolution and evaporating the second solvent. Following this technique,it is unnecessary and in some instances may be undesirable for thesolvent used to dissolve the herbicide to be the same as the solventused to dissolve the protective material. Under such circumstances, thesolvent may be selected for the herbicide without regard to its solvencyaction on the protective material, and vice versa. Thus Dicamba has beenapplied to attapulgite granules from an ethanol solution, the ethanolwas removed by evaporation, and a solution of petroleum asphalt (Pioneer180 Witco Chemical Co., 180 F. melting point) in hexane was applied andthe hexane removed by evaporation. The granular product was subjected tothe leaching test described with regard to the test of Table II and gaveresults essentially the same as those for the material of Example V.

While various support material have been disclosed previously for thecomposition of the present invention, a modified support material hasbeen found to provide exceptional results. Attapulgite granules,pre-coated with shellac, provide a carrier showing increased resistanceto dissipation of herbicidal composition contained therein. In a typicalexample of the preparation of such porous carrier, a 2% solution ofshellac in ethanol was employed to impregnate the attapulgite granules.After drying, the shellac-coated granules were coated with a toluenesolution of Dicamba and wood rosin. In a leaching test of the typedescribed herein with respect to Table II, the composition applied tothe precoated attapulgite showed very considerably less dissipation thanthe same combination applied directly to uncoated attapulgite. Thistechnique is particularly valuable with herbicides that tend to bereadily decomposed by the catalytic action of clay granules. A thinprecoating of oxidized asphalt similarly protects the herbicide andreduces dissipation of the herbicide from the composition. Theseshellac-precoated, and oxidized asphalt-precoated clay granules havealso been found to provide an excellent carrier for insecticides andfungicides and particularly for the phosphorothioate and insecticidessuch as 2 methyl Z-(methylthio) propionaldehyde O- (methylcarbamoyl)oxime. In general, the amount of said precoating should be from about0.2% to 20% by weight of the carrier.

There is no critical limit on the amount of herbicide employed in thecompositions of the present invention other than the convenience of theuser in order to obtain a satisfactory and effective dosage. In general,the herbicide can comprise from about 0.5% to 50% by weight of thecarrier, but preferably is from about 1.0% to about 10.0% by weight ofthe total composition. The amount of protective material employed willvary depending on the nature of the selected herbicide and the degree ofherbicide dissipation which can be tolerated and can range from about 2%to about by weight of the carrier. In general, however, the amount willrange from 1.0% to about 30% by weight of the total composition at aprotectant-to-herbicide ratio of 1:1 to 10:1. The protectant must bewater insoluble but soluble in a readily volatilized solvent. All of theuseful protectant should, of course, be essentially nonreactive with theherbicides, at least to the extent that it does not exhibit adeleterious affect on the herbicidal activity. Similarly, the carrierfor the composition should be essentially inert with regard to theherbicide.

What I claim is:

1. A process for preparing a herbicidal composition which comprises:

(A) dissolving an organic herbicide selected from the group consistingof 2-methoxy-3,6-dichlorobenzoic acid and 2,6-dichlorobenzonitrile and awater-insoluble, normally solid, fusible, non-reactive protectantmaterial in a volatile solvent selected from the group consisting ofbenzene, toluene and carbon tetrachloride in which both said herbicideand said protectant material are soluble, said protectant material beingselected from the group consisting of carnauba wax, oxidized petroleumasphalt, terpene resin and ozokerite wax,

(B) absorbing the resultant solution on an inert,

porous, granular carrier material comprising attapulgite granules whichhave been coated with a member selected from the group consisting ofshellac and oxidized asphalt,

(C) evaporating said solvent therefrom to provide a herbicidalcomposition wherein the herbicide, protectant and carrier material arein intimate association with each other, said composition containingfrom about 0.5% to about 50% of herbicide by weight of said carrier andfrom about 2% to about 80% of protectant by weight of said carrier.

2. A method for the preparation of a herbicidal composition comprisingthe steps of precoating attapulgite granules with shellac; impregnatingthe resulting granules with a toluene solution of2-methoxy-3,6-dichlorobenzoic acid; volatilizing therefrom said toluene;impregnating the granules with a hexane solution of water-insoluble,normally solid, fusible, non-reactive terpene resin; and volatilizingtherefrom said hexane.

3. A herbicidal composition comprising:

(A) an inert, porous, granular carrier material comprising attapulgitegranules having a precoating of a member selected from the groupconsisting of shellac and oxidized asphalt,

(B) a protective coating of a water-insoluble, normally solid, fusible,non-reactive protectant material selected from the group consisting ofcarnauba Wax, oxidized petroleum asphalt, terpene resin and ozo keritewax said protectant material containing an organic herbicide selectedfrom the group consisting of 2-methoxy-3,6-dichlorobenzoic acid and2,6-dichlorobenzonitrile, homogeneously dispersed therethrough,

( 1) said herbicide being present in an amount of from about 0.5% toabout 50% by weight of said carrier; and

(2) said protectant material being present in an amount from about 2% toabout 80% by weight of said carrier.

4. A herbicidal composition in accordance with claim 3, comprisingshellac-precoated attapulgite granules, 2- methoxy-3,6-dichlorobenzoicacid, and a water-insoluble, normally solid, fusible, non-reactiveterpene resin.

References Cited UNITED STATES PATENTS 14 Salvesen 71-100 Pierce 71-62Roberts et al. 71- 79 Wagner 71-115 McFadden et al. 424-78 Haden I r. etal 424-357 Yaife et a1. 424-278 Woodbury 424-218 FOREIGN PATENTS OTHERREFERENCES Weeds, Common and Chemical Names of Herbicides 15 (1967),vol. 15, No. 4 (October 1967).

LEWIS GO'ITS, Primary Examiner G. HOLLRAH, Assistant Examiner U.S.C1.X.R.

